To design a Proximal Tibial Model using the tibial component, the cancellous and the cortical bones; and assembling these three parts together.
Additionally, to construct a new bone and tibia assembly and run Finite Element Analysis (FEA) on the model using Pro Mechanica to determine the Maximum Principal Stress and the von- Mises Stress exerted by the model.
1. Effective kinematics restoration
2. Long term performance
3. Long term fixation
4. Installation with minimal damage to collateral structures
A total knee replacement is a surgical procedure whereby the diseased knee joint is replaced with artificial material.
The thigh bone (or femur) abuts the large bone of the lower leg (tibia) at the knee joint. During a total knee replacement, the end of the femur bone is removed and replaced with a metal shell.
The end of the lower leg bone (tibia) is also removed and replaced with a channeled plastic piece with a metal stem.
Depending on the condition of the kneecap portion of the knee joint, a plastic "button" may also be added under the kneecap surface.
Tibial tray and stem
High performance Cortical and Cancellous bone designs to fit the tibia
A/P and M/L curvatures match normal knee
Deep flexion ROM
Excellent range of tibia sizing options
FEA analysis on the proximal tibial model
Stress analysis and Results
The sizes applied to the tibial model are shown on the left. These are pretty standard and are observed in many commercial tibial systems.
These were referenced from the knee brochure from www.endotec.com
The cancellous and cortical bone Pro/E Designs were provided by Dr. Makris (BME Department, NJIT).
The designs were created by using a standard swept blend and sketch options in Pro/E.
The bones were then cutout using the cutout feature.
Both the bones were assembled together using the assembly creation in Pro/E.
01/28/10 Swept Blend
Here is the exploded view of the Proximal tibial assembly.
In Pro/E, the view can be saved in the View Manager>explode> new.
This view is called Explode1.
In the Applications section in Pro/E; click on Mechanica to run FEA
In Z-direction, apply a load of 100N on the top surface of the tibial component
Apply displacement constraint at the bottom of the bone
Assign the required materials and properties to the tibia and the bone
Run new static analysis for the results
01/28/10 Force = 100 N applied on the top surface of the tibia Displacement constraint at the bottom surface of the bone
Material used: TiAlly
Young’s Modulus = 117.2 GPa
Poisson’s Ratio = 0.33
Material properties used: Cancellous Bone
Young’s Modulus = 10.4 GPa
Poisson’s Ratio = 0.20
01/28/10 Components Von- Mises Stress (lbm/ (in sec 2 )) Maximum Principal Stress (lbm/ (in sec 2 )) Bone+ Tibia 3.318 e 2 1.084 e 2 Bone 8.887 e 1 3.142 e 1 Tibia 3.318 e 2 1.084 e 2
Tibial tray and stem constructed using the 10-32 thread
Cortical and Cancellous bone designs to fit the tibia
A/P and M/L curvatures would match the normal knee
Excellent range of tibia sizing options: SIZE 1 used (reference: www.endotec.com)
FEA analysis on the proximal tibial model completed
Stress analysis and Results obtained
Results show that the von-Mises stress and the Maximum Principal Stress are highest on the top surface of the tibia and the bottom curvature. This is understandable since the load is applied on the tibial surface. Also, the cutout on the bone shows a high stress due to the force applied on the tibia
The scope and design goals of the project are achieved. A Proximal tibial model with a tibial component, a cortical and a cancellous bone assembled together were used as a model to run the FEA.
The results of the FEA showed higher stress on the top surface of the tibial tray and the bottom curvature of the tibial stem as suspected